1. Field of the Invention
The present invention relates to an optical recording/reproducing apparatus of a type in which an alternative section can be readily accessed instead of a defective section.
A hard disk has been known as a recording/reproducing apparatus used with a magnetic head and capable of recording a relatively large amount of data.
Recently, an optical recording/reproducing apparatus, using an optical head as an alternative to a magnetic head and thereby capable of recording significantly more data than that recorded by a hard disc apparatus, has been put into practical use.
In the above-described optical recording/reproducing apparatus, a disc-like optical recording medium (to be called "an optical disk" hereinafter) is widely used.
If data written on the optical disk of the type described above cannot be correctly reproduced even though error correction processing has been conducted, alternative processing for rewriting the data in a different section (called "an alternative section") is performed.
That is, when the operation of writing in one sector of a plurality of sectors of each of the tracks of an optical disk has been performed with the purpose of recording data, an operation for verifying the data is conducted at the time the optical head scans the sector after the optical disk has rotated once for the purpose of confirming that the writing operation has been conducted correctly. If there are errors in the data after the data obtained from the above-described reading operation has been modulated, the errors are corrected by an error correction function. However, if the numbers of errors exceeds the correcting capacity or if an index portion, in which the address information of the sector in which data has been recorded is recorded, cannot be detected (identified), the controller determines that the sector is a defective sector and writes the same data in an alternative sector. The alternative sector may be positioned in the same track as that for the defective sector or on another track. In alternative processing of this type, the physical address of the defective sector and of the alternative sector are registered in a map (an SDL) in memory so as to be subjected to a reference in the next writing and reading operation. Technology of this type has been disclosed in Japanese Patent Laid-Open No. 60-205741.
According to the present invention, there is provided a hard disk apparatus comprising a usual convention sector and an alternative sector which is used instead of a defective user sector, whereby the defective sector can be replaced.
In the above-described alternation processing in which the map (the SDL) is used, if the alternative sector used instead of the defective sector also involves defects, the alternative sector must be alternated again. In this case, the map includes combinations of addresses of a plurality of the defective sectors and the addresses of alternative sectors. Therefore, in order to prevent the defective sector from being accessed for writing or reading, the sector which has been finally alternated must be accessed for writing or reading after all of the combinations of the defective sectors and the alternative sectors have been read out from the map so as to find the final alternative sector.
According to the above-described Japanese Patent Laid-Open No. 60-205741, the following operation is performed if the alternative sector is defective:
Assuming that sector (0.1)[0: track No., 1: sector No.] is the defective sector as shown in FIG. 1A, its alternative sector (1.0) is accessed for alternation. If the alternative sector (1.0) is defective, its alternative sector is further accessed for the alternation. Referring to FIG. IA, the sector which has finally succeeded in the alternation is alternative sector (1.3). As a result, the contents of a map in the memory becomes as shown in FIG. 1B. The forward 2 bits in the alternative sector indicative region serve as a flag, where [11] represents a fact that the alternative sector is defective while [01] represents a fact that its alternative sector has been succeeded in the alternative processing. Therefore, (1), (2) and (3) represent the fact that the alternative sector is defective, while (4) represents the sector which has been succeed in the alternative processing.
Then, when sector (0.1) is read referring to FIG. 1A, the controller examines the flag so as to determine whether or not the alternative sector corresponding to the defective sector can be used since sector (0.1) is a defective sector. Referring to FIG. 1B, since the thus specified alternative sector is also defective, the controller must again examine the map so as to read whether or not the further alternative sector can be used. As described above, in the case where the alternative sectors are successively defective, the flags of all of the corresponding alternative sectors must be read.
The above-described method renders the transfer rate to be lowered and the alternative processing to become too complicated as an external storage apparatus since the correspondence of the defective sectors and all of the corresponding alternative sectors must be examined.
Furthermore, the method of the above-described conventional examples cannot be applied to the case where the recording medium is replaced.